Antenna matching section



April 22, 1952 A. s. MEIER ETAL 2,593,474

ANTENNA MATCHING SECTION Filed Oct. 3, 1944 5 Sheets-Sheet l mvmpa Mm: man

A ril 22, 1952 A. s. MEIER ETAL 2,593,474

ANTENNA MATCHING SECTION Fil ed Oct. :5, 1944 5 Sheets-Sheet 2 A ril 22, 1952 A. s. MEIER ET AL 2,593,474

ANTENNA MATCHING SECTION Filed Oct. 5, 1944 s Sheets-Sheet s I N V EN TOR. 6215/76: Mf/[A 991/! 0. 6065/1140 Ap 1952 A. s. MEIER ETAL 2,593,474

ANTENNA MATCHING SECTION Filed Oct. 3, 1944 5 Sheets-Sheet 4 IN VEN TOR. 19115 5 076/674 194% 0. COAfflfA/V B Y $424249 &1,

A ril 22, 1952 A. s. MEIER ETAL 2,593,474

ANTENNA MATCHING SECTION Filed Oct. 3, 1944 5 Sheets-Sheet 5 tenna.

Patented Apr. 22, 1952 ANTENNA MATCHING SECTION Allen S. Meier, Xenia, and Paul D. Coleman, Dayton, Ohio, assignors to United States of America as represented by the Secretary of War Application October 3, 1944, Serial No. 557,037

(Granted under the act of March 3, 1883, as amended April 34], 1928; 370 0. G. 757) 4 Claims.

The invention described herein maybe manufactured and used by or for the Government for governmental purposes, without the payment to use of any royalty thereon.

This invention relates to antennas and more particularly to anantenna matchingsectionthat imparts broad band characteristics to the an- The objects of the present invention include the provision of an antenna matching section that a:

imparts improved performance to the antenna as compared with preexisting antennas, inthe broad band field, of an antenna ma'tchingfls'ection that imparts a maximum transfer of power to an antenna, and of an improved broad band antenna matching section that is of simple mechanical constructionand assembly and that consists of easily available components. I

With the above and other objects in view which will be apparent'to those who are familiar with antenna assemblies, suitable illustrative embodi ments of the present invention are shown'in' the accompanying drawing, wherein:

Fig. 1 is a fragmentary foreshortened side elevation of an antenna and matching section assembly that forms a part of the" subject matter of the present invention;

Fig. 2 .is an enlarged axial section taken along the line 22 of the" matching section of the antenna assembly that is shown in, Fig. l

Fig. 3 is a fragmentary axial section of the antenna assembly that is shown in 1 mounted upon the skin of a plane and withv its matching section coaxial cables foreshortened its indicate their connections;

Fig. 4 is an elevational view of the antenna assembly that is shown in Fig. 3 with parts broken away to disclose the mounting connections therefor; and

Fig. 5 is a side elevational view of a hollow antenna base support that serves to streamline and anchor an antenna assembly upon a mount.- ing surface therefor. The illustrative antenna, antenna matching sections, and mountings therefor, that areshown in the accompanying drawings as a physical embodiment of the present invention, employ readily available equipment in imparting broad band characteristics to usual types of antennas without increase in the conventional lateral dimensions of the antennas. v i

.A commonly availabl'ejwhip antenna of small lateral dimension has been chosen to illustrate an a tenna part of the present invention and may be replaced by other usual forms of lowwind'drag antennas without departing'from the present' i' vention. The antenna matching section that serves to impart broad band characteristics to ordinary types of low wind drag antennas also consists of readily available parts.

As shown in Figs. 1 and 3, the antenna I is threaded externally at its lower end to turn down into a centrally apertured grommet 2 that flares radially at its lower end to provide a flange portion 3 thereof. The grommet 2 is welded at its upper end to a thickened central part 4 of a hollow cylindrical matching section capping member 5. The grommet 2 is supported laterally in any desired manner, as by a thrust assuming support 6 or the like, that is interposed between the grommet 2 and the lateral wall of the capping member 5. A nut I and a washer 8 are disposed upon the cup member central part 4 and thread upon the antenna I to non-rotatably lock it in its engagement with the capping member 5. The

-= grommet flange 3 is apertured preferably axially to receive the upper or antenna input ends of two coaxial cable central wires I0 and I I that are disposed therein and that are connected electrically therewith, as by being soldered thereto or the like.

- Pins I2 are riveted to the member 5 at the ends of a common diameter for use in removably mounting the antenna assembly in place retractably from the inside of a plane fuselage.

The capping member 5 is secured in any suitable manner, as by rivets I3 to a radially outwardly extending ring I4. An upwardly open hollow housing I5 has its upper rim attached to the ring I4, by suitable means, such as by screws IS. A pair of bolts II extend axially of the housing I5 between the bottom of the housing I5 and the cap member 5 and carry bolt nuts l8 that are tightened thereon to assist in the support of the lengths of cable that are disposed within the housing I5.

Predetermined lengths of two coaxial cables that may be designated as a series transmission line and a shunt transmission line, are spirally wound within the interior of the matching section housing I5, as shown in Fig. 2, where they are supported radially by a cylindrical plate 20. A simplified presentation of the coaxial cables there disposed is shown in Fig. 3 of the drawings. As previously stated, the upper or antenna input ends of both of the center wires I0 and II of the two cables. are connected electrically to the antenna I thru the grommet 2.

The exposed woven outer conductor 2| of the series transmission line is insulated from the center wire I0 thereof by insulation material 21. The upper grounded end of the series line outer conductor 2| is soldered to the cap 5 and thereby grounded. The lower grounded end of the series line outer conductor 2| is disposed within a sleeve 22 which makes electrical contact with the bottom of the housing l5 and s grounded. The sleeve 22 and an outwardly accessible coaxial fitting 23 are secured to the bottom of the housing l by bolts 24. The lower or matching section input end of the center conductor I0 is connected to the center contact of the fitting 23.

The exposed woven outer conductor 25 of the shunt transmission line is insulated from the center wire ll by insulating material 28. The upper grounded end of the shunt line outer conductor 25 is soldered to the cap 5 and so grounded. The remote ends of both the center wire II and of the outer conductor 25 of the shunt line are short circuited and enclosed within a cap 25, The unattached end of the shunt line is short circuited when the line is one-quarter wave length and is open circuited when it is one-half wave length long.

The antenna and matching section assembly preferably carry a wave spring 39 and wear rin 3| that are disposed outwardly from the matching' section cap 5. The antenna and matching section assembly, as shown in Fig. 1, is adapted to be slidably inserted into a bayonet socket 32 that .is flanged radially outwardly at its upper end to overlie and be secured to a mounting surface, such as a ship skin 33 or the like, by means of a plurality of bolts 34, as shown in Figs. 4 and 5. The lateral sides of the bayonet socket 32 are slotted at 35 as shown to receive and releasably retain the pins [2 that extend radially outwardly from the matching section cap- 5 against the yielding axially directed pressure of the wave spring 39. V

A streamlined antenna supporting base 3% is also secured in place upon the surface of the ship skin 33 by the bolts 34 and nuts 39 as shown in Fig. 4 of'the drawing. A strut plate 31 within ent invention using a whip antenna is a considerable improvement over the results that'have been. accomplished in thepast with broad antennas based uponthe theorythatthe band width is1,a .function of the ratio of an antenna length to its diameter. The present,invention remcves the aerodynamically impractical excessive wind drag of antennas of large cross-sectional diameters that also are impractical for tactical reasons, and provides improved antennas for use in radio counter-measure applications at ultra high frequencies. For the type of work that the improved antenna that is disclosed herein is adapted to perform, an antenna that is based upon the older theory at fifty megacycles would have to be five feet in length and ten inches in diameter to produce a bandwidth of the order of forty percent. For high speed bombardment aircraft, this method of approach in order to obtain the necessary bandwidth is impractical.

.In the present invention the antenna imped since is matched by means of. a reactivenetwork at-the input end of the antenna; In this construction the shunt transmission line that consists of the inner wire I l and the outer conductor 25 substantially cancels the susceptance of the antenna, and the impedance level of the an tenna is stepped down or decreased substantially to that of the feed line by the series transmission line that consists of the inner wire In and the outer conductor 2|. This result is obtained with an illustrative assembly wherein a shunt line that is short circuited, is one-quarter wave length long, and that has a characteristic impedance of twenty-five ohms, is matched with a series line that is one-quarter wavelength long and that has an impedance of sixty-two ohms. With whip antennas that were fifty-four to seventy-two inches in length, and that were also mounted upon curved surfaces as presented in the patent application of Allen S. Meier for an Antenna, Serial No. 557,038, filed October 3, 1944, Patent No.

. 2,449,562, issued September 21, 1948, a conventional small-diameter antenna bandwidth was improved from 17.6 percent to 40 percent, a fac tor of 2.3. These antennas had a mismatch that did not exceed a two to one voltage standing wave ratio at a fifty ohm level over the band.

This construction also is used with antennas wherein the matching section consists of a halfwave open circuited shunt transmission line and a series quarter-wave transmission line. With this construction four parameters are involved which are chosen to produce a substantial gainin bandwidth. In addition to the above specified reflationship, a half-wave open circuited shunt transmission line and a half-wave series transmission line may be adopted with the parameters chosen to produce a substantial gain in band width. A quarter-wave short circuited shunt transmission line and a half-wave series transmission line may be combined with the parameters chosen to produce a material gain in bandwidth. j

The principle that is here involved has been proven experimentally to apply to whip antennas that are three-eighths of an inch in large diameter and that are from thirty to seventy-two inches in length, or antennas that have a length to diameter of one hundred to two hundred to one. These antennas have been matched with a matching section that has an impedance that gives a standing wave ratio of less thantwo to one over a forty percent bandwidth. The same principle would be applicable to antenna ratios of length to diameter of much smaller magnitude which would also result in corresponding increases in improved bandwidths.

The bandwidth of the antenna is increased by the choice of parameters of the transmission line elements. The parameters of the transmission line may be defined as the effective electrical length and characteristic impedance.

It is to be understood that the particular type of antenna and the particular form of matching section and the manner of its dispositionthat have been disclosed herein have been presented for the purposes of illustrating and explaining the present-invention and that other usual forms of antennas and that other forms and manner of connecting and housing the matching section may be adopted and used without departing from the present invention as defined by the appended claims.

What we claim is:

1. An antenna assembly, comprising in combination a whip antenna having a high impedance and a given susceptance and resonant bandwidth, and a matching section for said whip antenna, said matching section including a first spirally wound length of transmission line that is connected at one end to the input of said whip antenna and is adapted to energize said whip antenna by feeding radio energy thereto, said first line having a length such that the high impedance of said whip antenna is stepped down and its bandwidth increased, a second spirally wound length of transmission line connected at one end to the input of said whip antenna and in shunt with said first line, said second line having a length such that the susceptance of said whip antenna is cancelled out while its band- 1 width is broadened, said first and second spirally wound lines being encased in a substantially hollow housing having a cap at the top thereof that is adapted to lock with the base of said whip antenna, said housing being downwardly apertured, and a coaxial fitting having inner and outer portions insulated from one another, said fitting being receptive of radio energy and mounted in the aperture of said housing in a manner such that it is accessible from outside said housing, the outer portion of said fitting being electrically connected to said housing, said first and second lines each including inner and outer conductors insulated from one another, the outer conductor of said first line being electrically connected at one end to the cap of said housing and electrically connected at the other end thereof to the outer portion of said fitting, the inner conductor of said first line at said other end being electrically connected to the inner portion of said fitting, the outer conductor of said second line being electrically connected at one end to said cap, both said lines having said one end projecting through said cap, the inner conductors of said first and second lines being connected at said one end to the input of said whip antenna whereby said whip antenna will have a broad bandwidth.

2. The assembly of claim 1, further including means for short circuiting the inner and outer conductors of said second line at said other end thereof, and wherein said first and second lines have a length equal to one-quarter of a wavelength.

3. A matching network for a whip antenna having a high impedance and a given susceptance and resonant bandwidth, comprising in combination a substantially cylindrical, hollow, matching section housing that is capped at its upper end and downwardly apertured, a coaxial fitting having inner and outer portions insulated from one another, said fitting being receptive of radio energy and mounted in the aperture of said housing in a manner such that it is accessible from outside said housing, the outer portion of said fitting being electrically connected to said housing, first and second sections of spirally wound transmission lines, disposed within said housing and each having inner and outer conductors, the outer conductor of said first line being electrically connected at one end to the cap of said housing and electrically connected at the other end thereof to the outer portion of said fitting, the inner conductor of said first line at said other end being electrically connected to the inner portion of said fitting, the outer conductor of said second line being electrically connected at one end to said cap, both said lines having said one end projecting through said cap and being adapted to form a connection to the input of said Whip antenna, said first line having a predetermined length such that the impedance of said whip antenna is stepped down and its bandwidth increased, and said second line having a predetermined length such that the bandwidth of said whip antenna is increased while its susceptance is cancelled out.

4. The network of claim 3, further including means for short circuiting the inner and outer conductors of said second line at the other end thereof, and wherein said first and second lines have a length equal to one-quarter of a wavelength.

ALLEN S. MEIER. PAUL D. COLEMAN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,386,735 Schaefer Aug. 9, 1921 1,834,274 Fisher Dec. 1, 1931 2,085,434 Loftis June 29, 1937 2,086,976 Brown July 13, 1937 2,113,136 Hansell et al Apr. 5, 1938 2,147,807 Alford Feb. 21, 1939 2,158,271 Buschbeck May 16, 1939 2,158,875 Leeds May 6, 1939 2,193,859 Buschbeck Mar. 19, 1940 2,195,717 Cork et al Apr. 2, 1940 2,203,760 Wilckens June 11, 1940 2,238,438 Alford Apr. 15, 1941 2,311,472 Roosenstein Feb. 16, 1943 2,313,046 Bruce Mar. 19, 1943 2,354,314 Harsted July 25, 1944 2,354,809 Goldstlne Aug. 1, 1944 2,418,961 Wehner Apr. 15, 1947 

